These funds can trade at high premiums, and if you buy an ETF with a significant premium, you should expect to lose money when you sell. In general, ETFs do what they say they do and they do it well. But to say that there are no risks is to ignore reality. Liquidity is an important consideration when investing in exchange-traded funds (ETFs).
ETFs have different liquidity profiles for several reasons. Investing in an ETF with relatively low liquidity can cost you in terms of a wider supply and demand spread, a reduced opportunity to trade profitably and, in extreme cases, the inability to withdraw funds in certain situations, such as a major market crash.